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Topic: Plug chops and performance flops (Read 1408 times)

Greetings!I have been running my old Standard cast iron 350 as my daily commuting hack for all of 10 years now. She's always done well and has successfully traversed the north to south and east to west lengths of my country (India) with great aplomb and no fuss, albeit very leisurely.

She's got a custom made roller big end and that's the only mod she has till date. Done nearly 40,000 km on that particular job and about 1.35 lakh km since I bought her off her previous owner. Oh, and she dates back to 1980.

However, of late, she's been acting up. She gets up to 60 kph with no fuss whatsoever but then simply digs in and refuses to go any faster when given the stick. The revs climb, but very slowly, and the engine seems to have lost its fluff. I understand the lack of get-up-and-go that these bikes suffer from and I've been living with that for a decade now. If I need to go faster, my Yamaha is always at hand.

Anyhooo, on pulling open the plug, it was found to be a sooty black. I lowered the needle by one notch and the following was the result:

I realised it was a tad too lean so, I tightened the air screw in by 1/4th a turn. The result was the following:

There is no pinging and I had set the ignition timing with a dial gauge not too long ago. What could be the problem here?

I work on my own bike so please feel free to rattle away any tips that you might have and not the 'please ask the mechanic to check the following' kind of suggestions!

Reading the plugs can only help if you take a reading at a certain throttle opening(s) following the "drive at set throttle for a km or two atleast and then kill the ignition while riding and pop the plug" method. To make sure all the carb circuits are performing optimally. Randomly pulling the plug after a ride can not give a true picture about what the carb circuits are doing.

If you are running bone stock jetting, that should not be a cause for any concern. Best you can do is take the carb apart completely and clean it up real nice.

As for performance issues , check engine compression. That can tell something. 1.35 lakh km's is a fair bit and I'd expect a re-ring soon, if not already needed.

Thanks Ace! I too had a hunch that it could be related to a slightly retarded ignition timing. I'll do what the doc (you) ordered as soon as I get home from work tonight.

02Electra, thanks for the reply! What you said makes perfect sense, but I think my bike's got ample compression. It was re-ringed about 25,000 km ago and can take a lot of weight on the kicker at compression.

But all in, the plug colour looks about right, correct? Everybody and their uncles have varying opinions on what the much-in-demand 'brown' should look like.

Also, I've got a derelict Bullet 350 that I picked up a couple of years ago. I had intended on getting it readied for this one mother of a ride I had in mind. Other projects, including an old Tiger 90 and a Matchless GL got in the way.

Cutting a long story short, I intend to get this bike ship shape by March 2014. I have always restored motorcycles by the book, and my experience with performance mods is rather limited. So, I would like to propose the following: a Bullet 350 that will do well under sustained riding in hot and cold conditions, with a little more kick in the pants. I don't want a Yamaha Tenere but it would do well if I could ride something that will carry me and its own weight with dignity!

This is what I had thought of. Please do add/subtract wherever required:1. Lapped spigot and head to go gasketless2. Similar roller bearing big end as carried out on my regular commuter hack and occasional tourer.3. Oil cooler4. Free flowing exhaust5. Free flowing air filter6. Up-jetted carb7. Deburred ports in the head8. Losing unnecessary heavy bits like the deeply valenced mudguards and tool boxes9. Twin plug head (fuel quality will be utter crap, more akin to kerosene than petrol)10. A good solid carrier for my meagre worldly belongings

+1 I know when I was setting the timing on my EI conversion kit, it took a few attempts to get it where it would pull hard and NOT ping. And as you probably know, it doesn't take a lot of movement to make a significant change with the timing. If the timing does appear to be correct it is possible your carb may be dirty. If you haven't actually tore down and cleaned out the carb anytime recently (last year or two?), you may need to do so. It's possible your jets are getting gummed and varnished and not flowing fuel like they used to.

I would make sure you are getting good fuel flow and maybe try going up a size on the main jet. Has the temperature changed much lately where you are? I found my 350 was very sensitive to temp. changes and as soon as the temp dropped causing it to run lean it would lose the power it needed to run at speed, once the temps went up I would get some missing and sputtering telling me it was time to go back the smaller leaner jet....does your bike still have the extra airbleed on the plate between the carb and the engine?

if you are still running a points ignition that uses a mechanical advance you might make sure that is free to move and advancing properly...Good luck

That's not a bad idea. Perhaps the advance mechanism cable stretched or is even bound up. Definitely worth taking a peak at. For how many miles are on it, I'm sure the points plate just needs a slight adjustment. If it starts and runs fine with no backfires but has no power above 3000-4000 RPMs,(good grunt down low, but nothing at the top) that's usually a good indicator of retarded timing. Good news is it should be an easy fix.